Bug#481702: asterisk: Call quality on IAX significantly worse than SIP

[Lionel Elie Mamane]

On Sun, May 18, 2008 at 03:51:08AM +0200, Lionel Elie Mamane wrote:

> For calls between the same two asterisk boxes, IAX audio is choppy (a
> fraction of second of sudden silence every few seconds) ("iax2 show
> netstats" shows lost packets), but SIP audio is OK.

> this scenario is also choppy:

>  ekiga behind boxA-SIP-boxB-IAX-boxA-ZAP

This scenario gives good audio:

 ekiga-SIP-boxA-IAX-boxB

Which made me think of a jitter buffer problem, because in this
scenario Asterisk is not supposed to do any dejittering. Indeed,
iax.conf on boxA had:

jitterbuffer=yes
forcejitterbuffer=no

with

jitterbuffer=no

it works *much* better. The ZAP channel also had a jitterbuffer
enabled, but not forced. Maybe the two jitterbuffers were being active
at the same time? This would be the bug then. On the other hand,
disabling the jitter buffer on the zap channel, but enabling it in
iax.conf also gives losses. So I think there is really something wrong
with the jitterbuffer in chan_iax. Note that "iax2 show netstats"
shows very little jitter, on the order of "3" (I suppose the unit is
ms?), even with the lost packets.

> I checked that this is not solved by 1.4.19.2. It did not happen
> before I upgraded to 1.4.19.

On the other hand, it is not solved by downgrading to 1.4.18.1
neither. So probably 1.4.19 is not to blame after all.

-- 
Lionel